Traits

Traits linked to FGF8

fibroblast growth factor 8

The Human Phenotype Ontology links 180 traits to FGF8, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the nervous system

Trait	How often it is seen
Abnormal central motor function	Often (30–79%)
Abnormal corpus callosum morphology	Often (30–79%)
Abnormal morphology of the olfactory bulb	Often (30–79%)
Abnormal shape of brainstem	Often (30–79%)
Abnormal shape of midbrain	Often (30–79%)
Abnormality of the autonomic nervous system	Often (30–79%)
Absent speech development	Often (30–79%)
Anxiety	Often (30–79%)
Aplasia of the falx cerebri	Often (30–79%)
Attention deficit	Often (30–79%)
Behavioral abnormality	Often (30–79%)
Communication delay	Often (30–79%)
Depression	Often (30–79%)
Epilepsy	Often (30–79%)
Impulsivity	Often (30–79%)
Inability to walk	Often (30–79%)
Intellectual disability	Often (30–79%)
Irritability	Often (30–79%)
Lack of feeling, emotion, interest	Often (30–79%)
Lethargy	Often (30–79%)
Limb dystonia	Often (30–79%)
Neural tube defect	Often (30–79%)
Oromotor apraxia	Often (30–79%)
Poor speech	Often (30–79%)
Short attention span	Often (30–79%)
Sleep-wake cycle disturbance	Often (30–79%)
Specific learning disability	Often (30–79%)
Abnormal gait	Sometimes (5–29%)
Abnormal septum pellucidum morphology	Sometimes (5–29%)
Agenesis of corpus callosum	Sometimes (5–29%)
Ataxia	Sometimes (5–29%)
Difficulty articulating speech	Sometimes (5–29%)
Enlarged brain	Sometimes (5–29%)
Hand mirror movements	Sometimes (5–29%)
Holoprosencephaly	Sometimes (5–29%)
Hypoplasia of the pons	Sometimes (5–29%)
Leg paralysis	Sometimes (5–29%)
Perisylvian polymicrogyria	Sometimes (5–29%)
Rhombencephalosynapsis	Sometimes (5–29%)
Too much cerebrospinal fluid in the brain	Sometimes (5–29%)
Tremor	Sometimes (5–29%)

Abnormality of head or neck

Trait	How often it is seen
Blockage of the rear opening of the nasal cavity	Very often (80–99%)
Hyposmia	Very often (80–99%)
Lost smell	Very often (80–99%)
Midnasal stenosis	Very often (80–99%)
Only one upper front tooth	Very often (80–99%)
Abnormally small head	Often (30–79%)
Bifid uvula	Often (30–79%)
Central cleft upper lip	Often (30–79%)
Cleft palate	Often (30–79%)
Flat nose	Often (30–79%)
High palate	Often (30–79%)
Narrow nasal bridge	Often (30–79%)
Short philtrum	Often (30–79%)
Tented mouth	Often (30–79%)
Abnormal dentition	Sometimes (5–29%)
Big calvaria	Sometimes (5–29%)
Cleft lip	Sometimes (5–29%)
Cleft of the mouth	Sometimes (5–29%)
Decreased number of teeth	Sometimes (5–29%)
Depressed nasal bridge	Sometimes (5–29%)
Frontoethmoidal encephalocele	Sometimes (5–29%)
Mono nostril	Sometimes (5–29%)
Nasal tip, upturned	Sometimes (5–29%)
Proboscis	Sometimes (5–29%)
Short nose	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Decreased testicular size	Always
Primary amenorrhea	Always
Short penis	Always
Abnormal erection	Very often (80–99%)
Absent sperm in semen	Very often (80–99%)
Decreased fertility	Very often (80–99%)
Difficulty getting a full erection	Very often (80–99%)
Increased female sex drive	Very often (80–99%)
Non-obstructive azoospermia	Very often (80–99%)
Underdeveloped penis	Very often (80–99%)
Undescended testes	Very often (80–99%)
Previous menstrual periods stop	Often (30–79%)
Small uterus	Often (30–79%)
Underdeveloped ovary	Often (30–79%)
Abnormal morphology of female internal genitalia	Sometimes (5–29%)
Abnormality of the genitourinary system	Sometimes (5–29%)
Absent kidney	Sometimes (5–29%)
Ambiguous external genitalia	Sometimes (5–29%)
Dyspareunia	Sometimes (5–29%)
Infertility	Sometimes (5–29%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Delayed bone maturation	Very often (80–99%)
Abnormal vertebral morphology	Often (30–79%)
Abnormality of the ribs	Often (30–79%)
Decreased muscle tone in infant	Often (30–79%)
Generalized decreased muscle tone	Often (30–79%)
Involuntary muscle stiffness, contraction, or spasm	Often (30–79%)
Low solidness and mass of the bones	Often (30–79%)
Osteopenia	Often (30–79%)
Osteoporosis	Often (30–79%)
Abnormal skeletal development	Sometimes (5–29%)
Abnormality of the skeletal system	Sometimes (5–29%)
EMG: myopathic abnormalities	Sometimes (5–29%)
Flexed joint that cannot be straightened	Sometimes (5–29%)
Hypermobility of all joints	Sometimes (5–29%)
Low muscle tone	Sometimes (5–29%)
Low muscle tone in trunk	Sometimes (5–29%)
Muscle weakness	Sometimes (5–29%)
Permanent flexion of the finger or toe	Sometimes (5–29%)
Recurrent fractures	Sometimes (5–29%)
Scoliosis	Sometimes (5–29%)

Abnormality of the endocrine system

Trait	How often it is seen
Hypogonadotropic hypogonadism	Always
Absence of pubertal development	Very often (80–99%)
Absence of secondary sex characteristics	Very often (80–99%)
Anterior hypopituitarism	Very often (80–99%)
Decreased function of male gonad	Very often (80–99%)
Decreased serum testosterone level	Very often (80–99%)
Delayed puberty	Very often (80–99%)
Female hypogonadism	Very often (80–99%)
Gonadotropin-releasing hormone deficiency	Very often (80–99%)
Abnormal hypothalamus physiology	Often (30–79%)
Abnormality of the endocrine system	Often (30–79%)
Central diabetes insipidus	Often (30–79%)
Diabetes insipidus	Often (30–79%)
Early onset of puberty	Often (30–79%)
Central hypothyroidism	Sometimes (5–29%)
Decreased response to growth hormone stimulation test	Sometimes (5–29%)
Panhypopituitarism	Sometimes (5–29%)
Underactive thyroid	Sometimes (5–29%)
Small pituitary gland	Not recorded

Abnormality of the eye

Trait	How often it is seen
Abnormality of the eye	Very often (80–99%)
Abnormally close eyes	Very often (80–99%)
Cerebral visual impairment	Often (30–79%)
Abnormal color vision	Sometimes (5–29%)
Cat eye	Sometimes (5–29%)
Cross-eyed	Sometimes (5–29%)
Cyclops eye	Sometimes (5–29%)
Drooping upper eyelid	Sometimes (5–29%)
Involuntary, rapid, rhythmic eye movements	Sometimes (5–29%)
Visual impairment	Sometimes (5–29%)
Wide-set eyes	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Feeding difficulties	Very often (80–99%)
Poor suck	Very often (80–99%)
Acid reflux	Often (30–79%)
Constipation	Often (30–79%)
Poor swallowing	Often (30–79%)
Vomiting	Often (30–79%)
Abnormal shape of the digestive system	Sometimes (5–29%)
Absence or narrowing of first part of small bowel	Sometimes (5–29%)
Anteriorly placed anus	Sometimes (5–29%)
Gastrostomy tube feeding in infancy	Sometimes (5–29%)

Growth abnormality

Trait	How often it is seen
Eunuchoid habitus	Very often (80–99%)
Faltering weight	Very often (80–99%)
Growth delay	Very often (80–99%)
Short stature	Very often (80–99%)
Abnormality of body height	Often (30–79%)
Prenatal growth deficiency	Often (30–79%)
Obesity	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Abnormal cardiovascular system morphology	Sometimes (5–29%)
Abnormal heart rate variability	Sometimes (5–29%)
Abnormality of the heart	Sometimes (5–29%)
Narrowing of aorta	Sometimes (5–29%)
Strawberry mark	Sometimes (5–29%)
Tetralogy of Fallot	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Abnormality of limbs	Sometimes (5–29%)
Dropped arches	Sometimes (5–29%)
High-arched foot	Sometimes (5–29%)
Hip dislocation	Sometimes (5–29%)

Abnormality of the integument

Trait	How often it is seen
Limited armpit hair	Always
Sparse pubic hair	Always
Sparse body hair	Very often (80–99%)
Ichthyosis	Sometimes (5–29%)

Abnormality of the breast

Trait	How often it is seen
Underdeveloped breasts	Very often (80–99%)
Wide-spaced nipples	Very often (80–99%)
Enlarged male breast	Often (30–79%)

Abnormality of the respiratory system

Trait	How often it is seen
Abnormal pattern of respiration	Often (30–79%)
Central apnea	Often (30–79%)
Chronic lung disease	Often (30–79%)

Abnormality of the ear

Trait	How often it is seen
Sensorineural hearing impairment	Often (30–79%)
Congenital sensorineural hearing impairment	Sometimes (5–29%)

Abnormality of the immune system

Trait	How often it is seen
Aspiration pneumonia	Often (30–79%)
Asthma	Sometimes (5–29%)

Abnormality of prenatal development or birth

Trait	How often it is seen
Premature birth	Often (30–79%)

Abnormality of the voice

Trait	How often it is seen
Abnormality of the voice	Very often (80–99%)

Laboratory abnormality

Trait	How often it is seen
Temperature instability	Often (30–79%)

How often is among people with one of the gene's conditions, the most often across them, as the Human Phenotype Ontology records it. These pages describe traits and the research behind them; they are not a diagnosis, and a doctor or genetic counsellor is the person to ask about symptoms.

Where this comes from

The Human Phenotype Ontology, release 2026-09-01: the traits linked to FGF8 and how often each is seen. Find out more at hpo.jax.org.

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